Isotopes Flashcards

All 6 cards in this deck

What is meant by the mass number of an atom?

The total number of protons and neutrons in its nucleus.

What is meant by the atomic number of an atom?

The number of protons in its nucleus.

What are isotopes?

Atoms of the same element with the same number of protons but different numbers of neutrons.

Which number identifies an element, and why?

The atomic number (number of protons) — every atom of an element has the same number of protons and no other element has that number.

What are the steps to find the numbers of protons, neutrons and electrons in an atom from its nuclear symbol?
e.g. $^{23}_{11}\mathrm{Na}$

1. Protons = atomic number (bottom number): 11
2. Electrons = protons, as an atom is neutral: 11
3. Neutrons = mass number − atomic number: $23 - 11 = 12$

True or false? Isotopes of an element have different numbers of electrons.

False. They have the same numbers of protons and electrons, but different numbers of neutrons.